Radiant tube heaters are compact, self-contained direct heating devices. They can be used to heat factories, warehouses, foundries, gymnasiums, loading docks, race track stands, arena bleachers, outdoor restaurants, swimming pool surrounds and many other areas. Radiant tube heaters can also be used for snow melting and de-icing, as well as in car washes and other environments.
Infra-red energy is a form of electromagnetic (EM) radiation. It makes up a portion of the electromagnetic spectrum and has wavelengths close to the wavelengths of visible light, but infra-red energy cannot be seen by the human eye. Infra-red energy, like all EM radiation, travels in straight lines at the speed of light. EM radiation is line of sight, i.e., if the radiation source can be ‘seen’ by the object, the object will in turn receive the radiant energy.
Radiant tube heaters radiate infra-red energy which is absorbed by things with mass and whose surfaces are not highly reflective, such as floors and people. Intermediate transfer medium, such as air or water, are not needed nor are fans or pumps. As personnel, animals, floors and objects in the primary radiation pattern are warmed by the infra-red energy, they tend to transfer heat to the surroundings by conduction and convection.
In a radiant tube heater, an air and gas mixture enters the burner. Exhaust gases, generated by the combustion of air and gas, exit the burner. Positioned downstream of the burner is an elongated tube which carries the fan-blown hot air along the length of the elongated tube. As the hot air heats the tube, the tube begins to radiate heat to the surroundings. An open reflector, typically constructed of highly polished aluminum, further directs the infra-red rays to the target areas. Combustion contaminants are exhausted at the other end of the tube to the outside.
Radiant tube heaters provide several advantages over forced air heating systems, including lower fuel costs, less heat loss, faster heat generation, greater comfort at lower temperatures, out-of-the-way installation and unobtrusive operation.
There are already patents on radiant tube heaters. Most of these patents focus on the creation and management of the combustion, not the translation of that combustion heat in to radiant heat and transmission of radiant heat via the tube sizes or shapes coupled with a reflector shape. Reference is made to U.S. Pat. No. RE37,636 and its predecessor U.S. Pat. No. 5,353,986, both assigned to Detroit Radiant Products Company (Warren, Mich.). These patents are directed to 2-stage heat control in a radiant tube heater. Other prior-art patents include U.S. Pat. No. 4,645,450, assigned to Control Techtronics, Inc. (Harrisburg, Pa.), U.S. Pat. No. 5,112,217, assigned to Carrier Corporation (Syracuse, N.Y.), U.S. Pat. No. 4,869,229, and UK patent GB 2 189 314, assigned to Grayhill Blackheat LTD (United Kingdom).
A problem with the radiant heaters of the prior art is in the ability to control the amount and direction of heat to a desired location, generally the floor or lower area of a building. All radiant tube heaters discharge a certain amount of heat out the end of the tube, such that a tube heater is typically 70% or so efficient in taking input energy from the fuel and transforming that energy into useable radiant heat. Prior art heaters are intended largely for industrial applications where they are mounted high up in the structure. In a poultry house, for example, the ceiling height is relatively low, typically about 10 feet.
Further, radiant tube heaters typical of the prior art have higher tube temperatures at the start of the tube sections and lower tube temperatures towards the end of the tube sections resulting in variations in radiant energy over the length of the heater. Installing the radiant heater of the typical prior art in a poultry house results in excessively hot areas underneath the tubes at the start of the tube section with decreasing temperatures down the overall length. Additionally, tube heaters of the prior art when installed at the lower heights of a typical poultry house are limited in their ability to radiate heat sideways or across the house. This irregular ‘egg shaped’ heat pattern can be detrimental to the object being heated, i.e., poultry.
The object of the present invention is to create an improved version of a radiant tube heater to maximize radiant heat transfer in total from the product by changing temperature distribution down the length of the tube and maximizing ‘line of sight’ availability of the EM radiation at the floor level and to minimize or eliminate the traditional ‘egg-shaped’ pattern of radiation.